The name "atom" is translated from Greek as "indivisible." Everything around us - solids, liquids and air - is built from billions of these particles.
Atom version appears
For the first time, atoms became known in the 5th century BC, when the Greek philosopher Democritus suggested that matter consists of moving tiny particles. But then it was not possible to verify the version of their existence. And although no one could see these particles, the idea was discussed, because only in this way could scientists explain the processes taking place in the real world. Therefore, they believed in the existence of microparticles long before the time when they were able to prove this fact.
Only in the XIX century. they began to be analyzed as the smallest constituents of chemical elements having the specific properties of atoms - the ability to join compounds with others in a strictly designated amount. At the beginning of the 20th century, it was believed that atoms were the smallest particles of matter, until it was proved that they consist of even smaller units.
What does a chemical element consist of?
The atom of a chemical element is the microscopic building block of matter. The defining feature of this microparticle was the molecular mass of the atom. Only the discovery of the periodic law of Mendeleev substantiated that their species are diverse forms of a single matter. They are so small that they cannot be seen using ordinary microscopes, only the most powerful electronic devices. For comparison, the hair on a person’s hand is a million times wider.
The electronic structure of an atom has a nucleus consisting of neutrons and protons, as well as electrons, which revolve around the center in constant orbits, like planets around their stars. All of them are held together by electromagnetic force, one of the four main ones in the universe. Neutrons are particles with a neutral charge, protons are endowed with positive, and electrons are negative. The latter are attracted to positively charged protons, so they tend to stay in orbit.
Atom structure
In the central part there is a core filling the minimum part of the whole atom. But studies show that almost the entire mass (99.9%) is located in it. Each atom contains protons, neutrons, electrons. The number of rotating electrons in it is equal to the positive central charge. Particles with the same nuclear charge Z, but with different atomic masses A and the number of neutrons in the nucleus N are called isotopes, and with the same A and different Z and N - isobars. An electron is a minimal particle of a substance with a negative electric charge e = 1.6 · 10-19 coulomb. The charge of an ion determines the amount of lost or added electrons. The process of metamorphosis of a neutral atom into a charged ion is called ionization.
New version of the atom model
Physicists have discovered to date many other elementary particles. The electronic structure of the atom has a new version.
It is believed that protons and neutrons, no matter how small they are, consist of the smallest particles called quarks. They constitute a new atomic construction model. As scientists used to gather evidence for the existence of the previous model, today they are trying to prove the existence of quarks.
RTM - the device of the future
Modern scientists can see atomic particles of matter on a computer monitor, as well as move them on the surface using a special tool called a raster tunnel microscope (RTM).
This is a computerized tool with a tip that moves very carefully near the surface of the material. When the tip moves, the electrons move through the gap between the tip and the surface. Although the material looks completely smooth, it is actually uneven at the atomic level. A computer makes a map of the surface of a substance, creating an image of its particles, and scientists can thus see the properties of an atom.
Radioactive particles
Negatively charged ions circle around the nucleus at a fairly large distance. The structure of an atom is such that the whole atom is really neutral and does not have an electric charge, because all its particles (protons, neutrons, electrons) are in balance.
A radioactive atom is an element that can be easily cleaved. Its center consists of many protons and neutrons. The only exception is the scheme of the hydrogen atom, which has one single proton. The nucleus is surrounded by a cloud of electrons, it is their attraction that makes it rotate around the center. Protons repel each other with the same charge.
This is not a problem for most small particles that have several. But some of them are unstable, especially for large ones, such as uranium, which has 92 protons. Sometimes its center does not withstand such a load. They are called radioactive due to the fact that they emit several particles from their nucleus. After the unstable core got rid of the protons, the remaining ones form a new daughter. It can be stable depending on the number of protons in the new nucleus, and can be further divided. This process lasts until a stable child core remains.
Atomic properties
The physicochemical properties of an atom naturally change from one element to another. They are determined by the following main parameters.
Atomic mass. Since the main place of the microparticles is occupied by protons and neutrons, their sum determines the number expressed in atomic units of mass (amu) Formula: A = Z + N.
Atomic radius. The radius depends on the location of the element in the Mendeleev system, chemical bonds, the number of neighboring atoms and quantum-mechanical action. The radius of the nucleus is one hundred thousand times smaller than the radius of the element itself. The structure of an atom can lose electrons and turn into a positive ion or add electrons and become a negative ion.
In the periodic system of Mendeleev, any chemical element takes its established place. In the table, the size of the atom increases when moving from top to bottom and decreases when moving from left to right. From this, the smallest element is helium, and the largest is cesium.
Valence. The outer electron shell of an atom is called valence, and the electrons in it have received the corresponding name - valence electrons. Their number determines how an atom combines with the rest via a chemical bond. By the method of creating the last microparticles, they try to fill their outer valence shells.
Gravity, gravity - this is the force that keeps the planets in orbit, because of it the objects released from the hands fall to the floor. A person notices gravity more, but the electromagnetic action is many times more powerful. The force that attracts (or repels) charged particles in an atom is 1,000,000,000,000,000,000,000,000,000,000,000 times more powerful than gravity in it. But in the center of the nucleus there is an even more powerful force that can hold protons and neutrons together.
Reactions in nuclei create energy like in nuclear reactors, where atoms are split. The heavier the element, the more particles its atoms are built from. If we add the total number of protons and neutrons in the element, we learn its mass. For example, Uranus, the heaviest element in nature, has an atomic mass of 235 or 238.
Atom divisions
The energy levels of an atom are the amount of space around the nucleus where the electron is in motion. In total there are 7 orbitals corresponding to the number of periods in the periodic table. The more distant the location of the electron from the nucleus, the more significant energy reserve it possesses. The period number indicates the number of atomic orbitals around its core. For example, Potassium is an element of 4 periods, which means that it has 4 energy levels of the atom. The number of a chemical element corresponds to its charge and the number of electrons around the nucleus.
Atom is an energy source
Probably the most famous scientific formula was discovered by the German physicist Einstein. She argues that mass is nothing but a form of energy. Based on this theory, one can turn matter into energy and calculate by the formula how much it can be obtained. The first practical result of this transformation was atomic bombs, which were first tested in the desert of Los Alamos (USA), and then exploded over Japanese cities. And although only a seventh of the explosive turned into energy, the destructive power of the atomic bomb was terrible.
In order for the core to release its energy, it must be destroyed. To split it, it is necessary to act with a neutron from the outside. Then the core breaks up into two other, lighter, while providing a huge surge of energy. Fission leads to the release of other neutrons, and they continue to split other nuclei. The process turns into a chain reaction, resulting in a huge amount of energy.
Pros and cons of using a nuclear reaction in our time
The destructive force that is released during the transformation of matter, mankind is trying to tame at nuclear plants. Here, a nuclear reaction does not occur in the form of an explosion, but as a gradual transfer of heat.
The production of nuclear energy has its pros and cons. According to scientists, in order to maintain our civilization at a high level, it is necessary to use this huge source of energy. But it should be borne in mind that even the most modern developments cannot guarantee the complete safety of nuclear power plants. In addition, radioactive waste received during energy production during inappropriate storage can affect our descendants for tens of thousands of years.
After the accident at the Chernobyl nuclear power plant, more and more people consider the production of nuclear energy very dangerous for humanity. The only safe power plant of its kind is the Sun with its huge nuclear power. Scientists are developing all kinds of models of solar cells, and perhaps in the near future, humanity will be able to provide itself with safe atomic energy.